Rumors about Apple leaning towards sapphire covered displays have been around since 2012, but they have never actually turned out to be true. The company stil uses Gorilla Glass in all of its iPhones, it has used it in every iPhone that has been released since 2012. But in recent months there have been some developments that hint towards the possibility of Apple finally making the switch, such as the $578 million deal with GT Advanced Technologies for opening up a sapphire manufacturing plant in Arizona.

Initially reported by a Taiwanese publication, Foxconn is said to have manufactured 100 prototype units of the sapphire covered iPhone at a factory in the Longhua district of Shenzhen. If the rumor is true, then its certainly a major milestone for Foxconn. The manufacturing process would have been more complex with sapphire as opposed to Corning’s Gorilla Glass, Apple would need to assess if its manufacturers can cope up and maintain favorable yield if it is to go ahead with these plans.

It won’t be wise to speculate right now if the next generation iPhone is going to come with a sapphire covered display, while it remains a possibility, its simply too soon. A 100 unit prototype batch doesn’t exactly sing praises of the manufacturing ability, rather its more like a proof of concept.